ECG Flashcards
What are the three sets of “leads in an ECG?
Limb leads (I, II and III) Augmented limb leads (aVF, aVL, aVR) Praecordial leads (V1-V6)
In which intercostal space do V1 and V2 electrodes go?
4th IC space
Position of:
a) V4
b) V5
c) V6
a) 5th IC, mid clavicular line
b) 5th IC, ant. axillary line
c) 5th IC, mid axillary line
What do the limb leads form?
Einthovens triangle
Tracing problems in ECG (3)
AC interference
Muscle tremor
Baseline wander
Calculation used for rate
300 divided by number of big squares between two R waves
How can rate be calculated in patients with tachycardia?
1500 divided by number of small squares between R waves
How can rate be calculated when rhythm is irregular?
Count QRS complexes in 30 large squares, multiply by 10
What is the cardiac axis?
The “general direction” of depolarization within the heart
In a person with normal cardiac axis, which lead is usually a) the most positive and b) the most negative?
a) II (goes in same direction as depolarization)
b) aVR (goes in opposite direction)
Axis ranges:
a) normal
b) RAD
c) LAD
a) -30 to 90 degrees
b) 90 to 180 degrees
c) -30 to -90 degrees
Axis waveforms:
a) I, II and aVF positive
b) I negative, aVF positive
c) I positive, aVF negative
a) normal
b) RAD
c) LAD
Causes of LAD
Expiration
LBBB
Left anterior hemiblock
WPW syndrome
Normal PR interval?
120ms-200ms (three to five small squares)
What does a prolonged PR interval imply?
1st degree heart block
What does a shortened PR interval imply?
Unusually fast conduction via an accessory pathway e.g. WPW syndrome
Normal QRS duration
less than 120ms (three small squares)
What are the rhymth rules?
- Is there electrical activity?
- Is the rhythm regular?
- What is the heart rate?
- Are there P waves?
- What is the relationship between P waves and QRS complexes?
- What is the QRS duration?
